The present invention relates to anchors for use in the lifting of cast concrete products such as wall panels during the erection thereof. More particularly the invention relates to edge lift anchors.
In the fabrication of precast concrete wall panels either at an offsite casting yard or onsite, it is necessary to lift the panel from the horizontal configuration in which it is cast to a vertical configuration for transportation and/or erection. For offsite casting and for some onsite casting, lifting of the panel takes place from the edge of the panel which is the upper edge in the erected condition of the panel. For this purpose so-called edge lift anchors are incorporated into the reinforcing structure of the panel prior to casting. During casting the head of the anchor is encased within a removable or disposable void former to form within the edge surface of the panel a recess within which the head of the anchor lies for releasable coupling to lifting equipment.
Various forms of edge lift anchor are currently available. When the panel is being lifted when in its vertical configuration, the edge lift anchors must take the entire weight of the panel and edge lift anchors are appropriately sized for this purpose. Typically, the anchors are produced in a range of load carrying capacities from 2 tonne to 10 tonne, with anchors of appropriate capacity being selected for each particular job. For an anchor of given type and size, its load carrying capacity can be increased by the incorporation of an aperture beneath the head of the anchor to receive a tension bar which, conventionally, is a length of reinforcing bar which passes through the aperture and is bent to provide extending legs on either side of the body of the anchor to increase its effective depth of embedment relative to the upper edge of the panel. In a conventional tension bar, the loading is carried by the frictional forces between the bar and the concrete and for this reason, the legs of conventional tension bars tend to be of substantial length.